Process for dyeing nylon with acid dyes of limited solubility



E's. oaibrnmd mo, N mm A pmsror somnmn cm 1. McGrew'and William new s Wilmlntton, Del, sign N a co on a. r. as r nt c8 emours mum-warm,

'poration olDelawlre m in, Del nice!- No mum; Application July 2, me,

Serial mamas 6 Claims. (cl. 8-55);

. 1 v .This invention relates to the dyeing of textile fabrics, and more particularly to dyeing nylon fibers and fabrics.

'Inpresent commercial practice nylon is colored with-a class of dyestuiis kn invention has as an object a new and improved'process for dyeing nylon textile articles. A further object is aprocess for applying acid dyes uniformly on nylon yarn with evenness of and. without the resulting streaks and shade depth variations that. have previously characterized the acid dyeing of nylon fabrics. Other objects will appear hereinafter.

The above objects are accomplished by the method described below wherein the concentration 0! the dye ismaintained highly dilute by means of an aqueous dyebath in which the dye is the salt of an acid dyestutr having but slight I solubility in water.

We have discovered that the nylon fabrics, al-

though subject to the difllculties in dyeing noted above with dyeing processes which are applicable to other fabrics and which require readily soluble -dyestuif salts and their use in high concentration, are unii'ormly colored by conducting th dyeing in an aqueousdyebath in which the dyestufl salt is'one' which dissociates in the acqueo'us' dyebath fto' yieldadye anion concentration of at least 0.1 65

' 2 3 part per million but not greater than 50 parts per million based on'the weight of the dyebath.

of barium chloride equal to 100-1000% 01' the weight 01' the nylon to be dyed and the mixture is stirred. The nylon fabric is added and the bath heated to 50-100 C. for a period of one hour. The nylon is removed from the dyebath, rinsed,

differs by as much as 4%.

' tion is realized on fabrics prepared from yarns normal dyeing conditions, show wide variations in depth of shade.

To accomplish the same result by an alternative method the barium salt of the dyestuif is first the nylon, the fabric is removed from the bath.

The salts of the dyestufl used in the practice of this invention are of such low solubility that their d'yestufl is added can contain from 0% to 1000% barium chloride based on the fabric weight.

The synthetic linear polyamides known as nylon and the production of fibers and fabrics therefrom have been described in a number of United States patents and in particular in 3,071,250, 2,071,253 and 2,130,948. These fiberforming polycarbonamides described in the previ ously mentioned patents are obtained by several methods, forexample, by sch-polymerization of a dlamine, e. g., hexamethylenediamine or with a monoaminomonohydric alcohol, e. monoethanolamine, itbeing understood that these reactants can be replaced by their equivalent amide-forming derivatives. These linear polyarnides also include polyesteramides, for exam 1e, those obtained by.admixture with other linfar polymer-forming reactants, such as glycol-dib sic acid mixturesor mixtures of hydroxy acids, with yield the diamine the previously actants. On hydrolysis with hydrochloric acid,

the amino acid polymers yield the amino acid hydrochloride, the diamine-dibasic acid polymers hydrochloride and the dibasic carboxylic acid, and the amino alcohol-dibasic acid polymers yield the amino alcohol hydrochloride vand the dibasic 'carboxylic acid. In these polyamides the average number of carbon atoms separating he amide groups is at least 2. The preferred polyamides have an intrinsic viscosity of at least 0.4 (defined. as in Patent 2,130,948) and a unit length (defined in Patents 2,071,253 and 2,130,948) of at least 7.

The following examples are further illustrative of the practice of this invention. Parts are by weight unless otherwise stated.

.E'xample I A dyebath is prepared by addition of 50 parts of water of 0.014 part of 1-benzoylamino-2-methyl-i-W-naphthylamino anthraquinone carbazoie, 0.0025 part of milling yellow 56. conc. (color index No. 642), and 0.0025 part of alizarin blue black B (color index No, 1085). To this is added 50 parts of a calcium chloride solution (2.5 parts of CaClz) and 0.1 part of acetic acid. The calcium salts of the dye separate leaving a colorless supernatant solution. This is stirred manually to disperse the color throughout the bath. To the bath is introduced 2 parts of a section of knitted nylon fabric prepared from yarns drawn respectively 3.82 and 3.99 (a difference of 4%) times its length as spun from the molten polymer. The bath is heated to 80 C. and held there for one hour as the fabric is manually agitated. The fabric is removed, rinsed, and dried. Inspection of the dyed fabricshow it to be uniformly colored and devoid of spots or streaks and having no change in shade depth at the point where the yarns of different draw ratio were spliced together.

A similar section of nylon fabric knitted from the same yarns is dyed 1 hour at 80 C. with 0.014

part of 1-benzoyl-amino-2-methyl-4-p'-naph-- thylamino anthraquinone carbazole, 0.0025 part of milling yellow 5G, conc. (color index No. 642) and 0.0025 part of index No. 1085) in an aqueous bath (100 parts) containing 0.1 part of acetic acid. The resulting dyed section shows a marked increase in shade depth at the point where the yarn of draw ratio 3.99 was spliced to the yarn of draw ratio'3.82 during knitting. Neither of the dyed pieces shows a visually perceptible change when tested for washing fastness according to Test Method 1 on page 187 of the 1940 Year Book of the American Association of Textile Chemists and Colorists, Vol. XVII.

Example II A dyeing is conducted in the same manner as described in Example I'except the barium chloride is substituted for the calcium chloride. The resulting fabric is uniformly colored and shows complete absence of spots, streaks, and shade depth variations.

Example III A dyebath is prepared with the same dyes as given in Example I and in the same proportions. To this bath is added parts of barium chloride and 0.04 part of acetic acid. The nylon fabric to be dyed is knit from two yarns spun at different times, both of which are drawn 3.55 times original length and both are processed alike. .The

alizarin blue black B (color 4 yarns are chosen so that the knit fabric shows a change in shade depth four times as great'as that which is just perceptible to the eye at the point where they are spliced together when dyed by the conventional method as described-in the latter part of Example 1. Two parts of this knit fabric are added to the bath and the bath is heated to -85 C. for one hour and during this time the fabric is manually agitated. The nylon fabric is removed from the bath, rinsed, and

dried. Examination of the piece shows that it is evenly colored and contains no light-shaded areas or spots. I

Example IV subsequently condensing with p-toluene sulfonyl chloride, and 0.0007 part of the product obtained by coupling diazotized 4-amino-4'-methyldiphenylamine-z-sulfonic acid to a-naphthylamine followed by diazotization and coupling to-2-naphthol-6-sulfonic acid. A section of knit nylon fabric similar to that described in Example III and weighing two parts is introduced into this 'dyebath. The bath is heated to 80 C. in 15 min-. utes and maintained at 80-85 C. for one hour.

Practically all of the colorin the bath is taken up by the nylon. The nylon is removed from the I bath, rinsed, and dried. It is uniformly colored, i. e., completely devoid of spots, streaks and shade depth variations. Dyeing a similar piece of fabric by conventionalmethods using the same dyes leads to a section of fabric that is much more deeply colored on one side than on the other. In the practice of this invention the most important factor is the solubility of the salt of the 4 dyestuif employed. Also important are the properties of the dyestuff itself, the cation employed,

and the dyeing conditions under which the scantly soluble salt is used. These factors are all interdependent as willbe explained.

It is preferred toemploy salts of acid colors which dissociate inwater to the extent of supplying 0.1.to 50 parts per million based on the dyebath of dye anion. This corresponds to a dye anion concentration no greater than 10" moles per liter. Therefore, salts with asolubility prodnot constant of at least 10- and not greater than 10- usually give better dyeings. However, satisfactory dyeings are obtained with salts having solubility product constants as high as 10-,.par-

ticularly if an excess of the precipitating cation isused at the same time to further reduce the concentration of the dye anion by the principle of mass action.

It has been found most convenient to use calcium o1: barium ions to form slightly soluble salts of acid and direct dyestuffs for use in'dyeing as described in this invention. These cations are perfectly satisfactory, for the great majority of acid and direct colors.

direct dyestufl's, for example various alkaline earth metals such as strontium, and aliphatic,

addition to parts 1 However, other cations also formsalts of low solubility with acid and ammonium, hexylammonium, cycloheirylammonium, dicyclohexylammonium, di(p-ammonium cyclohexyl) methane, phenylammonium etc. ions. Certain other metallic ions such as 'ions of lead, aluminum, and magnesium form dye salts which meet the solubility requirements just recited. Some of these salts are less soluble than others and since such a wide range of precipitating cations is available, satisfactory combinations for all acid and direct dyestuffs can be obtained that will come within the solubility limits described above. a

The character of the dyestuif has an important bearing also. For example, monobasic dyestuffs, i. e., containing one sulfonic acid group, form less soluble salts with alkaline earth metals and organic bases than do polybasic dyestufis. Howments for applying heat.

ever, these polybasic dyestuffs can be utilized in the practice of this invention although in some cases it is desirable to use the mass action principle to reduce solubility as described earlier.

Satisfactory coverage of variations in yarn dyeing properties are ordinarily obtained with calcium or barium salts of practically all acid and direct dyes using as much as 100 to 1000% calcium chloride or barium chloride based on the weight of the nylon in the dyebath. In some cases where the calcium or barium salts do not meet the solubility limits given above, salts of di(p-ammonium cyclohexyl) methane, which meet solubility requirements with all but a very few acid and direct colors, are employed.

Dyeing conditions under which these scantly soluble salts of acid dyestuffs can be used vary quite Widely. For example, they may be employed in baths in the pH range of 2-7 and at temperatures of 50-100 C. Temperatures greater than 100 C. may be used if the dyeing is done in pressure equipment. At low pH values, i. e., in the neighborhood of 24.5 it is not necessary to use excess barium chloride in the dyebath to suppress ionization of the salt with most colors whereas at higher pH values, 1. e., 4.5-7, a substantial excess of the cation is necessary to result in uniform application of dye despite variations in the yarn. Temperature variations are not critical as any temperature from 20 C. to 100 C. can be used but for convenience it is preferred to keep within the range of 50-100 0. so that dyeing will be complete in 1 to 2 hours or less.

To obtain best uniformity with a minimum of agitation during dyeing' it is desired to have the slightly soluble dye salt in a very fine state of subdivision so that a stable dispersion of the pigment may be prepared. Under such conditions the method of this invention 'is limited to substantially the same quantities that may be applied by conventional methods. That is, the use of dye salts of low solubility neither increases nor decreases the ability of nylon to absorb dyestuff but constitutes a process for applying uniformly on nylon the same amounts of color as can be applied by usual methods.

The apparatus used in the practice of this invention is of conventional type and should be designed to agitate the fabric and have arrange- I Any of the various machines now in use for textile coloration are satisfactory.

It will be seen from the foregoing description that this invention provides a practical and economical method for effecting uniform application of washfast acid and direct dyestuffs on nylon yarns and fabrics even though wide variations in amount of dye take-up are encountered when dyed by conventional methods, regardless of the causes of these variations.

As many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not to be limited to specific embodiments thereof, except as defined in the appended claims. Y

the particles will perfuse the fabric completely and not be subject to any filtering action on the part of the fabric. To assist in preparation of stable dispersions of dye salts, dispersing agents may be used. This may be done by addition of the dispersing agent to the solution of dye before the precipitating cation is introduced to form the dye salt of low solubility or by treatment of the dye salt in a ball mill with an aqueous solution of the dispersing agent. Either non-ionic, cationic or anionic type dispersing agents may be used as illustrated respectively by polyvinylalcohol, dodecyl trimethylammonium bromide, and partially neutralized polymethacrylic acid,

The amount of dyestufl that may be applied by We claim:

1. A process for evenly dyeing nylon textile articles which comprises immersing the nylon article, until the desired depth in shade is obtained, in an aqueous dyebath in which the coloring material is a salt of an acid dyestuff which dissociates in the aqueous dyebath to yield a dye anion concentration of at least 0.1 part per million but not greater than 50 parts per million I based on the weight of the dyebath.

2. The process set forth in claim 1 in which the coloring material is an alkaline earth metal salt of an acid dyestuff.

3. The process set forth in claim 1 in which said salt is a salt of the acid dyestuff with a multivalent metal ion. I

4. The process set forth in claim 1 in which said salt is the barium salt of the acid dyestufl".

5. The process set forth in claim 1 in which said salt is the calcium salt of the acid dyestuff.

6. The process set forth in claim 1 in which said salt is the lead salt of the acid dyestufi.

FRANK c. McGREW, WILLIAM HENRY SHARKEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Badische (F'r.) Addition 12,403 (2nd addition to basic Patent 297,330) June 20, 1910. 

